A short circuit after some successful testing


#1

I've got the image ok on the cape and updated the arduino code.

I did some good diagnostics of my setup with some different wall wart style power adaptors. A 12V and also a 24V. I think I will need to reprogram my esc's as the down and ctrl keys werent doing anything but other than that everything was going ok.

All of a sudden my 24V power adaptor seemed unhappy and stopped working, which was puzzling. I also noticed one of the caps of a motor got hot enough to melt the glue gun glue a bit.

That should have been warning enough to stop there but I wanted to test the battery setup and so I put 6 of the batteryspace 3.7V li-ion cells in series in the battery tubes. When I plug the molex connector together I noticed a very visible spark within the connector, at the ground wire of the power pin.

I cut off my plug connector thinking it was causing the short but that wasnt it.

The cape and beaglebone seem ok. I can still load the page and the camera by supplying 5V to beaglebone.

Is there something in a motor that blew up then? Other? I'm looking to get a handle on what is going on.


#2

Hey Frank,

Although the BeagleBone can handle up to 40v, the ESCs are only spec’d to tolerate about 12v. It sounds to me like you were driving them directly with 24v, and that may have caused one to fail closed. Brian has done some tests where he has powered his ESCs with upwards of 20v, but he may have just been luckey. I recommend removing the ESC that got hot, and trying everything then. You may have to replace that one.

Also, if you want to run your ROV with those lithium batteries (which I recommended), I suggest you rewire your battery packs to be in parallel, so that the whole system only gets 11.1v.

I hope this helps!

Eric


#3

ah ok! Yes I was focused on the specs of the cape. (I feel like I knew this about the esc's when I originally ordered them but spaced out last night). Will get ahold of some more then and thanks for the quick reply.


#4

Man this was a dumb move :-) But I am gettting going again - A heads up on something: I ordered and received the last 2 18A-SL/30935 Turnigy ESC's from the US Hobby King warehouse. I need one more. I was looking at the international hobby king site and it looks like those esc's are being discontinued and are being replaced by these:

http://www.hobbyking.com/hobbyking/store/uh_viewitem.asp?idproduct=...

It looks like they are slightly different - will these work for OpenROV?


#5

I've seen the same thing, and i think these will work also.

there could be that there are some slight differences with regards to the setup. its a shame that HK don't have the instructions available so we could check.


#6

We bought those (the TrackStar) ESC's for our OpenROV, but haven't gotten them wired up to test yet. We'll update as soon as they are (or aren't) running.


#7

if you could do a scan or high-res picture of the instructions that come with them, i could fairly quick see if they are equal or not.


#8

I don't have a camera or scanner handy, but I'll type up what I think are the relevant parts:

Specifications

Controls, TRACKSTAR Fwd/Brk or Fwd/Brk/Reverse
Input Power (Cells) 2-3S LiPo, 4-12 NiCd/NiMH
Brake Proportional
On Resistance, Brushless 0.002 Ohm Per Phase
Continuous/Burst Current 25 Amp/90 Amp
Linear BEC 5 Volts, 1 Amp
Status LED 1 with 3 color
Thermal Overload Protection Yes

As far as the programming options go, I can set it to allow full reverse and braking, various "punch" (acceleration) control settings, set drag brake (if the motor can move while the throttle is neutral), dead band for throttle, voltage cutoff at 5 6 9 or 12 volts (or can be disabled), and three motor timing settings ranging from efficient to high performance.


#9

I noticed the BEC voltage is different between the two ESC's.

The old one provides 6V BEC while the new one Provides 5V.

I do not know how these two will play together unless you can disable the BEC on the new ESC. Maybe someone can provide more insight on this.


#10

I plan to just use three of the new ones. Frank, you might want to just return the two you got and switch over to the new ones too.


#11

if you compare the settings list to this setting list: http://wiki.openrov.com/index.php/Programming_the_ESC

do you have the "3" mode on item 1? this is the function to go straight from forward to reverse. this is quite important.

is there other settings that you would be able to set compared to the list? the items and values are often equal across different esc's


#12

bec can normaly not be disabled. you would need to cut/remove the red wire from the connector going to the cape.

one CANNOT combine the esc's without removing the red wire on either the two 6v bec's or on the one with 5volt.

connecting these with 5 and 6volt together can destroy the bec function and the escs!


#13

Yes you can set it to go straight from forward to reverse. I think it's basically all the same kinds of settings. I'll scan when I get home today.


#14

thank you for checking. its important that we are sure of these things so we dont get in problems.

The main difference looks to be the 5v bec. 5v is more common, and we dont have that potential problem with the P13 jumper on the cape with the 6v bec on the old esc's

I've been thinking about trying one of the 10amp esc's from HK. these look really small and nice. we have so low power consumption for each motor anyway.


#15

I just ordered 6 of the Trackstar-type of ESC to try out (of course I'll report back with what I find!)

Also, I can't reply to your latest comment, Thomas (because it's too many replies into the thread, but I'm very interested in how the 10A ESC works out. Right now, the set of ESCs are the second most expensive part of the ROV, so if it's unnecessary to use the larger ones, that would be great! In practice, we've found that we rarely need more then 6A per motor since we limit the throttle to a servo value of around 130 (which draws around 5.5A in water) anyway.

Eric